The present invention generally relates to a motor-driven manipulating instrument adaptable for being programmed to repeatedly execute a predetermined series of spatial movements. In particular, the present invention is directed to a novel apparatus for generating a series of signals indicative of the specific movements of the instrument, which signals are adaptable for establishing a control program to control the drive motors and hence the movement of the instrument itself.
A manipulating robot instrument usually includes a control arm assembly formed from a plurality of attached members, with a hand attached to an end of the arm assembly for performing predetermined manipulations. For example, the hand may be employed in precision welding of two auto body parts to one another, thereby freeing a human operator from performing the repetitive and often boring task. However, in order to perform such work tasks, the robot hand must be able to precisely and repeatedly follow a predetermined spatial track.
One such known rotor assembly includes a composite arm assembly which can perform linear movement along two mutually perpendicular axes as well as rotation about one of the axes. As a result, the arm assembly is capable of executing a swiveling movement by combining the linear and rotative movements discussed hereabove. Furthermore, a hand member attached to such a known robot arm assembly can be rotated about an axis extending in the axial direction of the arm assembly as well as being rotatable about separate axes extending perpendicularly to each of the mutually perpendicular axes, respectively. Finally, a plurality of separate drive motors are arranged for driving the various component members of the arm assembly as well as the attached hand member.
In order to control the movement of the arm assembly, a control program is required for actuating the various drive motors in a predetermined sequence. In the known robot arm assembly, the desired track is usually divided into a series of linear sections, allowing the track curve to be approximated by straight-line linear movements which can be mathematically programmed. However, such mathematically originated programs are very complex and costly and, more importantly, can only roughly approximate the desired track.
In an effort to provide an assembly which more faithfully reproduces the desired spatial track, a further known robot arm assembly suggests that an elaborate template assembly surround the composite robot arm and hand assembly. The template assembly is formed from a plurality of seperate members which are positioned to follow the precise movements of the aggregate robot arm assembly. The template assembly carries a plurality of switches which are selectively activated upon contact with the various components of the rotor arm assembly. When activated, the switches close an electrical circuit which provides a signal indicative of a specific robot arm movement; with the signals being used to establish a control program for actuating the robot arm drive motors.
The exceedingly complicated layout of the above-referenced template assembly greatly increases the cost of programming the robot arm. In addition, an unavoidable time play must exist between the movement of the individual rotor arm members and activation of the various switch members, resulting in a significant variation between the actual movements of the rotor arm and the program generated by actuation of the switches. Furthermore, a further error or fault in programming is directly caused by the dead weight of the template itself, which dead weight can result in switch activation without a corresponding movement of the robot arm. In fact, actual tests have shown that such programming faults tend to lead to the robot arm following so-called jumpy or step curves rather than the continuous curves often required in welding operations or the like. The outlay required to compensate for such jumpy or step movements have made the use of a template commercially unacceptable.
As will be discussed in detail hereafter, the present invention provides an apparatus capable of precisely following the manual manipulations of a robot arm assembly and of generating a signal corresponding to such manipulations, which signal is adaptable for establishing a control program to control the robot arm drive motors for repeatedly manipulating the arm assembly.